Colorado scientists have produced a genetically pure Yellowstone bison, launching an embryo transfer project to resurrect wild herds that 100 years ago nearly went extinct.

The 125-pound reddish-brown male calf unveiled Thursday at the Bronx Zoo in New York is expected to be the first of many bison that do not carry genetic traits of cattle.

Zoo officials say they’re working with conservationists to acquire vast tracts of prairie grasslands around the western U.S. — land where newly engineered pure herds can graze, wallow and propagate.

The idea is to produce enough calves to also supply other zoos and species conservation groups working to restore bison herds, said Pat Thomas, curator and associate director of the Bronx Zoo. Most of the 200,000 or so bison in North America today are genetically tainted due to interbreeding with cattle.

“What we would not want to do is have the bison that we hope to reproduce here come into direct contact with bison that have small amounts of domestic cow genes,” Thomas said. “If they breed, then what we’ve done to create a pure herd would be undone.”

The project began in October when Colorado State University researchers flushed the embryo from a bison brought to Fort Collins from Yellowstone National Park — home of North America’s largest remaining herd of purebred bison. The removal of bison from the 4,000 headYellowstone herd has been heavily restricted due to cattle industry concerns that bison could spred brucellosis, which could infect cattle and people.

However, about 30 were released last year to the U.S. Department of Agriculture as a “restoration herd” that was quarantined at a closed facility in Fort Collins.

The CSU team extracted the embryo and chemically “washed” it, removing disease. The herd in transition had picked up Johne’s disease. Then, CSU technicians implanted the embryo into the uterus of a healthy bison that carried cattle genes.

CSU researchers in April loaded that impregnated, 850-pound surrogate mother, with 15 familiar bison, onto a trailer. A truck towed them to another closed facility at the Bronx Zoo in New York.

The pure-bred calf was born on June 20.

Bison embryo transplantation “gives us an avenue to bring out genetics that have been isolated for a long time,” CSU reproductive physiologist Jennifer Barfield said.

“This could be used for a lot of different species. It provides us a way to create new offspring where it was previously impossible or very difficult. We’re able to create new animals that can be used by zoos starting herds and to help expand populations that need it,” Barfield said. “The possibilities are endless.”

A Texas professor tested the DNA of the bison that produced the embryo, Barfield said, and has verified they carried no cattle genes. Proof that the calf is pure “should be a sure thing,” she said.

The Bronx Zoo, run by the Wildlife Conservation Society, has led species conservation efforts worldwide. CSU and zoo officials planned to transplant up to 16 more Yellowstone bison embryos next month. This time, they’ll do the embryo insertions in New York.

Bison calves eventually will be sent to western preserves where bison once roamed widely, Thomas said. Project participants include American Prairie Reserve, a Montana-based group working to acquire 3 million acres with native vegetation that, when combined with adjacent public lands, can be a haven for bison along with elk, deer, pronghorn, bobcats and snakes.

“Any time you apply a technique to a new species, there’s going to be uncertaintly. We thrilled this (embryo transfer) was successful,” Thomas said, praising the CSU team.

A century ago, hunting by humans brought bison to the brink of extinction with fewer than 1,100 left. Settlers shot bison from trains. Previously, tens of millions of bison roamed North America.

New York conservationists began trying to save bison in 1907, sending bison survivors west in hopes they’d create new herds. But the western ranchers who nurtured surviving bison relied on interbreeding with cattle to try to increase bison numbers.

Today, wild bison number around 19,820 nationwide, according to the Denver-based National Bison Association. An estimated 198,000 bison are raised on ranches for hides and meat.

Denver maintains a municipal bison herd that was established in 1914, using bison hauled from Yellowstone. Today, about 55 bison graze behind 12-foot fences topped with barbed wire in city parks – bred from ancestors who were domesticated after mixing with cattle.

But some now act wild. Denver bison calves increasingly are born with humps on their backs, distinct from flat- backed cattle. City herd supervisors have observed that, when coyotes approach, the bison band together with bulls on patrol — reverting to wild herd behavior.

Bruce Finley covers environment issues, the land air and water struggles shaping Colorado and the West. Finley grew up in Colorado, graduated from Stanford, then earned masters degrees in international relations as a Fulbright scholar in Britain and in journalism at Northwestern. He is also a lawyer and previously handled international news with on-site reporting in 40 countries.

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